1. Field of the Invention
The present invention relates to a medical guide wire used for treatment of a vascular lesion or the like.
2. Description Related to the Prior Art
Conventionally, a medical guide wire (hereinafter simply referred to as the guide wire) has been used for radial dilation (radial expansion) of a vascular lesion such as a vascular occluded portion or a stenotic portion. The guide wire has a single coil or coaxial inner and outer coils in a distal end portion of a core. The distal end portion of the guide wire is inserted into a blood vessel and advances in the blood vessel until it reaches a lesion. Thereby a radial dilation treatment of the vascular lesion is performed. The radial dilation treatment expands the diameter of the vascular lesion or the like.
The guide wire needs plastic deformation properties and rotation transmission capability to advance in a desired direction in a tortuous blood vessel of complicated structure or at a blood vessel branch. Capability of the guide wire to advance in a desired direction at the blood vessel branch or the like is referred to as the selection capability. The plastic deformation properties represent performance to bend and plastically deform an extreme end portion of the guide wire in a shape of a letter “J” or an inverted letter “J”. The rotation transmission capability represents performance of the guide wire to rotate the inserted core and the distal end portion of the guide wire through the coil(s) partially fixed to the core, by rotating a proximal portion (rear end portion) of the guide wire outside of the body.
Japanese Patent Laid-Open Publication No. 08-317989 discloses a guide wire of a double coil structure in which an outer coil is disposed outside of and concentrically with an inner coil through which a core is inserted.
U.S. Pat. No. 5,144,959 (corresponding to Japanese Patent Laid-Open Publication No. 03-133463) discloses a guide wire of a double coil structure with outer and inner coils provided at a distal end of a thin flexible axis. The outer diameter of the inner coil is smaller than the inner diameter of the outer coil.
The Japanese Patent Laid-Open Publication No. 08-317989 only discloses technical principles to improve the rotation transmission capability of the guide wire through the use of a radiopaque member for the inner coil, stainless steel, a shape-memory alloy, or the like for the outer coil, and a resilient member (such as that used for spring) for the core.
The U.S. Pat. No. 5,144,959 only discloses technical principles to improve visual inspection properties in observation mainly in a radiation transmission method. In the U.S. Pat. No. 5,144,959. the inner coil with the outer diameter smaller than the inner diameter of the outer coil is formed of a radiopaque member, in a manner similar to the Japanese Patent Laid-Open Publication No. 08-317989.
Hence, the above-described references do not disclose technical principles for improvements in the rotation transmission capability and the flexibility, owing to winding directions of the outer and inner coils, improvements in the plastic deformation properties, owing to space wound portions provided in corresponding positions at the distal ends of the outer and inner coils, respectively, and improvements in the rotation transmission capability to transmit the rotation to the distal side, owing to a tapered middle portion provided to each of the outer and inner coils and the use of an outer diameter ratio between the maximum outer diameter and the minimum outer diameter, or the like.